Rational Design of Dendritic Phase-Pure Tin Antimonide Intermetallic Film-Based Negatrodes for Commercially-Viable Flexible Sodium-Ion Pouch Cell Battery

Exploiting the ability to directly deposit larger-sized, flexible, alloying-type sodium-ion battery electrodes without the need of additional inactive components and processing steps is a strategic way to achieve higher gravimetric capacities which will be suitable for commercial-level sodium-ion (SIB) pouch cell manufacturing. In this regard, a simple, template-free electroplating protocol is reported for designing phase-pure tin antimonide (TA)-based negatrode. An optimum control over the potentiostatic electroplating parameters allows the preferential formation of dendritic nanostructures over an electroplated foam-based current collector. The prepared negatrode and Mn-based Prussian blue analog positrode in full coin cell format deliver an average nominal working voltage of 3.0 V with a discharge energy density of 342 Wh kg⁻¹. In single-layer full pouch cell format, an 8.01 mAh capacity (89.89 mAh g⁻¹, 593.3 µAh cm⁻²) is achieved at an undeformed state and 97.12% capacity is retained at 180° bend condition. In multi-layer full pouch cell format, a 35.86 mAh capacity (80.58 mAh g⁻¹, 531.2 µAh cm⁻²) is achieved with 62.77% capacity retention after 200 cycles (0.125 C). The results of this work showcase how a simple, template free, aqueous electrolyte based electroplating protocol can be developed for the direct fabrication of large-sized, flexible, alloying-type negatrodes for commercial SIB pouch cells.